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Publisher/Editor: II. D. Cheek. Sr. aka “Or. tmrm>rtis" V1N1<: Noveaber-Deceaber. 1991

THE WORLD SCANNER REPORT

A Journal of VHF-UHF Scanner Technology i Engineering

GROSS IGNORANCE & SHEER STUPIDITY

Humble pie. The subscription blank that appeared in the
last few issues was thoroughly confusing with good reason
since it was designed for new subscribers with no thought
given to renewals. The blank on the inside of the back
page has been revised to be easier to understand and fill
out. Back Issues are under one heading; current subs are
under a separate one now. If, for any reason, you feel
that you were shortchanged by the confusion, let us know
and we'll make it right. Standard policy is to issue a
refund for overpayment, but let us know if that's not
satisfactory. The new sub blank & prices are current and
supersede all others. Apologies for imbecilic idiocy.

LAST CALL TO RENEW FOR 1992

Check the Expiration Date on your mailing label; if it
says "Nov 91", this will be the last issue you'll receive
until you renew. A fluorescent color will highlight that
part of your label as a reminder of impending expiration.
1992 is shaping up to be a great year for unleashing the
power of your scanner. You won't want to miss out! Renew
right away before you forget! Thanks to those who have
renewed early. Cindy, our Administrator, is delighted to
have the work spaced out instead of piled up all at once.

THIS IS THE LAST ISSUE OF 1991

This is the 10th and last issue of 1991. The WSR is
published 10 times per year to allow for Staff Holidays
and uninterrupted periods of R & D for coming issues.
January, 1992, begins our second year with V2N1 to be
mailed on or around Jan-1, but slight delays caused by
the holidays are to be expected. The mails will be slow
(and so will we). By February, we’ll be back on track to
mail each issue during the last week of the month. Thank
you for a great 1991. Your support and acclaim were the
booster stages that put us into low orbit. Next year,
the moon; and then the planets and the stars

WANTED TO BUY: A CHEAP COMPUTER

We're looking for a very cheap IBM/clone MSDOS computer,
either 8088 or 80286 based. Minimum requirements are
640-k RAM, one or more floppy drives; monochrome; one
serial and one parallel port. Desirable options might
include a hard drive, modem, CGA/VGA , etc. Our budget
for 1992 includes a serious 386 or 486 computer but a
rock-bottom priced model of the above description is
needed NOW so that we can begin the final phases of
research on Computer Interfaces for the PRO-2004/5/6.
R&D is always expensive, so costs have to be kept down.
If you have or know of a very cheap computer available,

please speed your offer immediately. Serious offers with
our minimum needs will be considered. For those who
don’t know, we've been Apple-based for many years while
IBM & MSDOS passed us by. It's clearly evident that an
Apple Interface for scanners won’t be well received;
hence our need for a simple and inexpensive IBM/clone
developmental machine.

THE LATEST ON COMPUTER INTERFACES

The need for easy computer programming of scanners with
400 or more channels is self evident now. One round of
manually punching in 400-channels, only to discover that
an inadvertent missed frequency at Ch-47 will be enough
to make you see the Cosmic Light. If you’ve done the
3200, 6400 or 25,600 Channel Mods, that Light will be
blinding. Would you believe that computer interfacing of
the PRO-2004/5/6 is actually "old hat" now? Two or three
years ago a fellow advertised in "Monitoring Times” plans
for a Commodore 64/128-PRO-2004 interface . I mentioned
this to a digital guru, Lin Burke, who then whipped up a
functional interface for the Radio Shack Color Computer
II. He went on to modify it and the associated BASIC
program for my Apple. No problem. Then came a design by
Miles Abernathy for the Macintosh computer. We converted
the design and its BASIC control program for my Apple.
Lots of work and cost but it was done. Two things these
three interfaces had in common was ONE-WAY communication
with the scanner and a computer-specific BASIC program to
run the interface.

More recently comes a universal interface kit from RW
Systems and an MSDOS-specif ic interface package including
software from DataMetrics, Inc. The kit from RW Systems
is promising because (1) it appears to be universal for
most computers and (2) computer-specific software is not
required to run it. It requires only a serial port and a
routine telecom program for operation. DataMetrics'
package is complete, ready to install in any MSDOS
computer with 640-k RAM and a parallel port. While the
DataMetrics' package works only in IBM/clones, it is
driven by commercial software; the interface is easy to
install and appears to be foolproof in operation. Both
the kit from RW Systems and the package from DataMetrics'
appear to be two-way devices in the sense that the
computer can log and store events from the scanner. RW
Systems’ kit appears to be functional for any of the
PRO-2004/5/6 series, while DataMetrics specifies that
theirs is for the PRO-2006 only. I think it is a safe
bet that it will work just fine in the PRO-2005 and can
be easily adapted to the PRO-2004, but DataMetrics does
not support any but the PRO-2006 at this time. I will be
evaluating RW Systems’ kit and the DataMetrics package in
the coming weeks. Perhaps we will have an opinion to

offer in the next issue. If you want specs & prices in
the interim, contact the companies as follows and tell
them you were referred by the "WORLD SCANNER REPORT".

DATAMETR ICS, INC RW SYSTEMS

2575 SOUTH BAYSHORE DR; STE-8A PO BOX 910(543

COCONUT GROVE, FL 33133 SAN DIEGO, CA 92191

Two of the three one-way interfaces discussed above are
not commercial ventures so the circuits & BASIC programs
can appear here in future issues if interest warrants.
There may be other designs for interfaces that we'll
publish, too, as there seems to be a wealth of info and
interest circulating now. We will confine our main focus
to those interfaces, commercial or public-domain, which
give the most for the least and which require a minimum
of effort on the hobbyist to install and operate. I have
a feeling there will be dozens to look at in the coming
year, so a certain amount of focus on our part will be
necessary. A key focus will be on the TWO-WAY interface;
i.e, one that not only programs the scanner's memory
banks, but also which can pass data from the scanner to
the computer for logging of active freqs, lengths of
transmissions, dates, times, etc. To my way of thinking,
the most important side of an interface is that which
programs the scanner's memory banks, thereby sparing us
the drudgery and opportunity for error. This alone will

free up time to enjoy the benefits of our scanners. But

if enjoyment is what this business is all about, then we

have to look at the other side of the coin: data logging

& processing. Half the fun of scanning is in the

listening to what's going on, but the other half is in
the accumulation of knowledge and understanding of radio
communications. The side of an interface that passes

data from the scanner to the computer for logging,
processing and storage is the long term benefit while the
actual monitoring is a short term benefit. Therefore, we
will look at both sides of a scanner-computer interface
in the coming year. Speaking of both sides, there are a
limited number of ways to obtain data FROM the scanner,
perhaps only two. DataMetrics found one way that might
never have occurred to me; HB Technologies is breaking
ground on the only other way that seems possible at the
moment: decoding the data from the scanner's CPU to the
LCD Display! That data stream contains most everything
pertinent to scanning with exception of time and date.
The trick is to decode it, since some of that data is
superfluous and some is for the PLL circuits but the boys
over at HB Technologies seem to have deciphered the stuff
for the LCD Display and what's more, they’re about to
show you how you can do it for yourself.

A SERIAL DATA I NTERCEPTOR/DEOODER FOR THE
PRO- 2004/5/6 CPU/LCD DISPLAY DRIVER

By: B.Bond/HB Technologies

This article describes in detail an actual circuit that
can "view'' data transferred from the PRO-200X CPU to the
LCD control ler/driver 1C. The circuit is elementary in
nature and lends itself well to both practicality and
cost limitations. A drawback of this approach is that

the device (referred herein as the GBL) relies heavily on
manual interpretation of captured data. IC’s comprising
the GBL are described as follows:

74HC164 - Ser ial - 1 n/Paral I el -Out (SIPO). Takes a serial
byte of data and converts it to parallel format.

74C14 - Hex Schmitt triggers (inverting). Inverts BUSY\
for use as a write pulse (W\) in addition to generating
a read pulse (R\) at the DS2009 FIFO (below).

DS2009 - A 512 x 9 bit First- In/First-Out (FIFO). Used to
store the data and C/D\ flag from the CPU.

MC14495 - Hex/7-segment decoder. Converts the hexadecimal
data from the FIFO to 7-segment for LED display.

Waveforms used by the GBL

RESET - Used to reset both the uPD7225 and DS2009 .
Generated by IC-503 (Scanner CPU) at power-up.

BU$Y\ - Inverted and used to perform FIFO write
operations. Generated by UPD7225 and goes high upon
receipt of CS\ (chip select) low from the CPU. BUSY\
remains high for duration of byte transfer and returns
low when the UPD7225 is ready to receive the next data
byte.

W\ - FIFO write pulse. Leading edge of W\ initializes
write. Trailing edge writes data.

SI - Serial data input from CPU. Presented to SIPO and
clocked by SCK\.

C/D\ - Control/Data (not) flag. When C/D\ is a logic low,
the data transferred from the CPU is a display byte,
whereas a logic high represents a command byte. Used
within the UPD7225 for data routing and by the GBL for
data differentiation.

R\ - Read pulse for retrieving data stored within the
FIFO. Also latches display data within the Hex/7-segment
decoders.

FF\ - FIFO full flag. Logic low indicates that the FIFO
is full and no further writes may be performed. Logic
high permits additional writes.

EF\ - FIFO empty flag. Logic low indicates that the FIFO
read pointer has returned to the write pointer location
following a read operation.

The GBL operation begins with the reset pulse from the
CPU. Reset causes both the internal FIFO read and write
pointers to reset to the bottom of the memory stack.
BUSY\ goes high (driven by C$\ low) prior to data-send
causing W\ to go low and initialize a FIFO write. 8 bits
of data are sequentially clocked into the SIPO by 8 SCK\
clock pulses. The most significant bit of the data byte
will be at the QH output of the SIPO following the 8th

CP. Within 9-usec of the 1st CP, C/D\ will be setup. At
this time, the data byte and flag (C/D\) will be present
at the FIFO inputs D0-D8. After the 8th CP, UPD7225 pulls
BUSY\ low and routes the byte to internal registers.
This action causes W\ to go high, writing the byte and
associated flag into the FIFO. Having transferred the
byte, UPD7225 returns a BUSY\ high, allowing subsequent
byte transfers. Readout of the FIFO content is initiated
by R / pulses which present and latch the data to decoders
which drive a dual 7-segment display. Note: C/D\ drives
the RH decimal point of the most significant character
and is not latched. Consequently, the flag is present
only for the duration of the read switch depression
before the FIFO output is returned to a high impedance
state (release of FIFO read switch).

Because of the rapid data rate, the FIFO is quickly
overflowed during dynamic scanner functions (i.e. Scan,
Search, etc). This limits the GBL user to initiating
discrete functions, trapping the bytes, interpreting the
data, and lastly, ascertaining what areas of the memory
stacks internal to the UPD7225 are affected. In addition
to the transfer speed, the fact that several bytes are
Display, compounds the problem of automating an analyzer.
The reason is that 9 bits are required to properly ID a
byte and UARTs are good for only 5,6,7, or 8 bits. Below
are example bytes used within the UPD7225:

BYTE DEFINITION

42 mode set command which configures the 1C as a
quadruplexed driver.

20 clears display RAM.

11 enable display.

EX 1 1 1 D4 D3 D2 D1 D0; load data pointer w/ 5 bits of
X=Dn immediate data.

DX 1 1 0 1 D3 D2 D1 D0; write 4 bits of immediate data
X=Dn to the display RAM area addressed by the pointer and
increment pointer.

AX 1 0 1 0 D3 D2 D1 D0 , or blinking RAM addressed by
X=Dn pointer with immediate data. Write results to same
address, increment pointer.

Part sources: DS2009, MC14495, Allied Electronics,

(800) 433-5700; 74C14, 74HC164, Easy Tech; (800) 582-4044
or Digi-Key (800) 344-4539

This concludes an overview of mapping & decoding serial
data from the TxD port of the PRO-2004/5/6 CPU. This
info is provided for the benefit of those engineers and
technical people who want to contribute to the budding
science of interfacing the PRO-2004/5/6 to a computer.

j EDITORlS NOTE: I do not pretend to fully understand all

the content of this article and therefore probably cannot
answer questions about it. You can address questions to
8. Bond, c/o Editor , "WORLD SCANNER REPORT", and I will

forward to him for reply. Meanwhile, check this issue
for a schematic diagram of the GBL Data Analyzer and if
not present, it will be included next month. It was lost
in the US Mail as of this editing, /be]

FEATURE PRESENTATION #1
A TONE DECODER/REJECTOR FOR SCANNERS

Just as the goal of the Computer Interface Project is to
enhance the fun and enjoyment of scanning, so too is this
neat modification for your scanner! Are you aware of the
concerted effort and conspiracy to deprive hobbyists of
some of that enjoyment? Government agencies and police
departments are especially guilty of this conspiracy when
the rascals spend millions of our tax dollars to encrypt
their communications. It is fortunate that many of the
conspirators can't afford the "unbreakable" DES/DVP
encryption systems, but this doesn't dissuade them from
taking a stab at other methods of depriving hobbyists of
their pleasure! Take for example, the nasty, nuisance
tones we hear on some transmissions nowadays. Some of
these signals are computer data communications, but
others are nothing more than pure tones sent out between
real transmissions so as to cause scanners to lock up on
them. What could be more obnoxious than loud, unabated
squeals? In the space of a few seconds, any sane and
sober scannist in full possession of his faculties will
punch the LOCKOUT button to preserve the family peace and
general state of mind. (Mission accomplished!)

The Toronto, Ontario, metro police agencies were among
the first around the world to implement "anti-scanner”
tones between transmissions to deter routine monitoring
of their communications. The cost was negligible; the
effect was monumental. Who, but a lunatic, would monitor
a 2-3 KHz piercing tone for hours on end? The public-at-
large sure won't. It wasn't long before the radio wizards
of Toronto designed a circuit to defeat the anti-scanner
tones and I am pleased to offer a variant of what they
call the "Metro Mod". I evaluated one version of the
Metro Mod as submitted by Mervyn DeGeer and found that it
had a few problems so I redesigned it and tested it for
hours. With no known bugs, my Tone Decoder/Rejector (TDR)
is offered for your evaluation and sadistic use.

My TDR uses an LM-567 Tone Decoder chip and a few parts
to detect a single tone of your selection. The TDR is
sensitive ONLY to the preselected tone and ignores other
sounds in the audio spectrum. When that tone comes in,
the TDR quickly reacts to force a $QUELCH-$et and thereby
fool the scanner into resuming SCAN or SEARCH. If the
scanner is in the MANUAL mode monitoring a frequency
which has the offending tone, the SQUELCH will not break
until the nuisance tone disappears and a voice signal is
present. If the scanner is SCANning or SEARCHing, it
won't even pause on a channel that has the offending
tone, but it will still stop and monitor any voice and
other transmissions that don't have the preset tone! The
tone to be rejected is set by adjustment of a trim pot,
VR-1, until the offending tone disappears!

There are no known liabilities or bugs in the TDR, but
there are limitations; it's good for only one essentially
pure and steady tone at a time which must be roughly
between 500 Hz and 5 KHz. The TDR will not respond well,
if at all, to warbles, repetitions, or data tones such as

for FSK, FAX & computers. If you identify two or more
different anti-scanner tones in use around the spectrum,
then you'll have to use one TDR for each tone; else reset
the one TDR for whatever single tone disinterests you the
most at a given time. If your tone-rejection needs are
lower than 500 Hz or higher than 5 KHz, a variation of
the design will be necessary. Likewise, two or more TDRs
working together may require a slight revision of a part
of the design. For now, let’s designate my TDR solely to
reject a single tone. If your needs are more complex, we
can discuss pertinent revisions in subsequent issues.

There is another situation where my TDR won't fully
apply. Some agencies transmit a tone along WITH voice
transmissions. Notch filters in their receivers remove
the tone leaving only voice to the speaker. My TDR will
not remove the tone and still allow the voice to be heard
in this type of "anti-scanner" measure. The TDR will
prevent the scanner from locking up on such signals,
however. To that extent, the TDR will preserve your
sanity even though you won't hear the voice signals. I
would like to hear from you folks who are plagued with
the "tone with voice" attempt at encryption, and if
enough of you respond, I will design a notch filter to
block such tones and still let voice through. By and
large, the "tone between transmissions" is the more
prevalent "anti-scanner" measure, and is for what my TDR
is designed. Ok, let's get to work and build one.

First, you have to select the correct TDR circuit. Refer
to last month’s issue, V1N9, Table 2, page 6 for the
NFM/AM chip that's in your scanner, and look in the far
right column of that table for the type of SQUELCH Logic.
If yours is Logic 0 when Squelch is Set, and 5,6, or 8v
when Squelch is Broke, then select the Type 1 TDR . If
your scanner's logic is just the opposite with Logic 5, 6
or 8v when SQUELCH is Set, and 0 when Squelch is Broke,
then select the Type 2 TDR . If there is any doubt on
which TDR is for your scanner, a simple test will decide
for you: set the scanner to a quiet channel (no signals),
and connect a volt meter between scanner ground and the
SCAN CONTROL pin of your scanner’s NFM/AM chip. See
Table 1 below for the correct pin # for your specific
NFM/AM chip. Now, set the SQUELCH control so that all
noise is silenced, and read the voltage at the SCAN
CONTROL pin. Then rotate the SQUELCH control so that
static noise can be heard and again read the voltage at
the SCAN CONTROL pin. If the first reading was 0-v and
the second, between 5 & 8v, you'll need the Type 1 TDR.
If your measurements were just the opposite, then yours
is the Type 2 TDR. The PRO-2004/5/6 and most Realistic
scanners will use the Type 1 TDR while most Uniden &
Bearcat scanners need Type 2, but be sure first, before
jumping in headlong. There’s not much difference between
the two TDR's but Type 2 requires one transistor and two
more resistors than Type 1. The TDR is easily assembled
on perf board about an inch square. Layout is not
critical, but follow the schematic diagram for the sake
of simplicity. It's not complicated.

The TDR was rigidly tested on the PRO-2004/5/6 & PRO-34

"THE WORLD SCANNER REPORT" (c)

scanners but it will work with most any scanner that uses
an NFM/AM chip like we've discussed so often in past
issues. There are 4 connections to the scanner: ground;
+5v; and two to the NFM/AM chip, "Detector Out" pin and
the "Scan Control" pin. Refer to last month's issue,
V1N9, Table 2, page 6 for the NFM/AM chip that's in your
scanner and then to Table 1 below for the Pins to which
you'll connect the TDR:

Table 1: TDR Connections

NFM/AM
Chip Type

Scan

Control

Detector

Out

Notes

TK 10420

PRO-2004/5/6; PRO-34/37

TK10421D-2

Cobra SR-15

TK10421M-2

BC-100/200/205/855XLT

MC3357P

Realistic, Regency,

MC3359P

BC-800XLT; BC-100XL

MC3361N

Realistic; AOR

NJM3359D-A

BC-400/560/760/950XLT

Install the Tone Decoder /Rejector board in a handy, out
of the way place in the scanner. If you anticipate the
need to occasionally adjust for different tones, then
consider a regular potentiometer with an external shaft
for VR-1. Another good idea and one which I often employ
is to drill a hole in the front panel of the scanner and
super-glue a trim pot behind the hole for a convenient
but unobtrusive screwdriver adjustment. Otherwise, VR-1
can be a trimpot on the perf board of the TDR. I suppose
you could dispense with S-1 and let the TDR run full
time, but if you want to be in total control of things,
install the switch where it can be readily reached.

The LM-567 chip is specified for a maximum of 9-volt dc
power, but you don't want to go to the limit when there's
no need. Most scanners nowadays have regulated +5vdc so
use it if you can. Otherwise, the operating voltage will
not be critical between 5-8 vdc. Connect the TDR power
point (Pin 4) to +5v via the DPDT switch. Make sure the
TDR board is well grounded. Solder R-2 directly to the
"Detector Out” or "Recovered Audio” pin of the NFM/AM
chip instead of putting it on the TDR board. Connect a
wire from the free end of R-2 to the free end of C-1 on
the TDR board. Solder a wire to the output (U-1, Pin 8,
Type 1 or collector of Q-1, Type 2) of the TDR, but don't
connect it to the NFM/AM chip’s "Scan Control" pin just
yet. We'll first test the TDR to make sure it works.

Preset VR-1 to one end of its rotation. Attach a volt
meter between scanner ground and the free loose end of
the TDR output wire. Turn on the scanner and the TDR.
Set the scanner to a frequency that has an obnoxious tone
that you wish would go away. The voltage at the TDR
(Type 1) output should be equal to the supply voltage or
aboutT volts. For Type 2 TDR's, the voltage will be
about 0 volts. Now, slowly adjust VR-1 thru it’s range;
at some point, that voltage should suddenly change; for
Type 1 ' s it will drop to nearly zero volts and for Type
2 ' s it will rise to 5-v. Continue adjusting VR-1 and the
voltage should change back to where it was before.

1991; V1N10 - Nov-Dec, 1991; Page 4

TYPE 1 TONE DECODER/REJECTOR CIRCUIT

The dropout point (Type 1) or peak point (Type 2) is the
tone-reject point of the TDR.

If your tests are successful at this point, then solder
the TDR output wire to the "scan control" pin of the
NFM/AM chip. Again slowly adjust VR-1 thru its range
until the offending tone just disappears. Tweak VR-1
back and forth to determine the middle of the dropout
zone and leave it set there. Operate the scanner as
normal with a welcome feeling of sheer relief!

Now a bit of theory for those who want to know how this
sucker works. The LM-567 chip is the key to it all. It

is rather complex on the inside, but with 8-pins on the
outside, one for ground and one for power, it is very
easy to use. In lay terms, the 567 is a "tone decoder”,
where the resistance between pins 5 & 6 and capacitance
from pin 6 to ground determine the tone to be decoded.
The equation for the tone is given as:
j where:

1 1 f 0 is the tone, hertz

fo = (VR1)(C4) 1 VR1 is resistance, ohms and

j C4 is capacitance, farads

Suppose that VR-1 is set to 2 , 500-ohms and C-4 is 0.2-uF,
then: f, = 1 / (2,500)( .2 x 10-*) = 1 / .0005
= 2000 Hz

Obviously, changing the value of VR-1 or C-4 will change
the tone to be decoded. The 567 is rated for a range of
frequencies from about 0.01 Hz to 500 KHz. For our use,
we need only a 'range of maybe 500 Hz to 5 KHz, so VR-1
and C-4 were selected accordingly. The Bandwidth of the
tone decoder can be varied somewhat by the value of the
capacitor, C-2. The smaller the capacitor, the wider the
bandwidth. Too small of a C-2, and the bandwidth will be
so narrow that VR-1 will be touchy and hard to set. Too
large of a value of C-2, and the TDR will cover too much
range and result in "falsing" or reaction to desirable
signals. The design here is good as is but the variables
are explained in case you find a use for it in some other
situation. A neat chip, the 567.

VR-1 and C-4 set a specific tone to be detected. The
audio output of the NFM/AM chip is applied to the input
of the TDR via R-2 and C-1 to Pin 3. As long as the

preset tone is not present, the 567 does nothing and the

output at Pin 8 is high at about 5 volts. When the

preset tone enters Pin 3, the 567 instantly detects it

and changes its output at Pin 8 from high to low or 0v.
This 2-state logic is used to discriminate among sounds.
For Type 1 scanners, the "high" output of the TDR makes
the scanner do nothing but act normal. When the preset
tone comes in, the output at Pin 8 goes low to force a
synthetic SQUELCH-Set at the NFM/AM chip's SCAN CONTROL
pin. This forced SQUELCH-Set blanks the sound and the
scanner will resume SCAN or SEARCH. Type 2 scanners have
an inverse Squelch Logic, so Q-1 inverts the 567’s output
logic to match. When the 567's Pin 8 output to Q-1 is
high, the collector output of Q-1 is low and vice versa.
It is as simple as that; a logic inverter.

Ckt

Svm Description

U-1 LM-567; NE-567; ECG/NTE-832; SK9089; R/S 276-1721

XU-1 1C socket, 8-pin DIP; R/S 276-1995
C-1, 3 Capacitors; 0.01-uF; R/S 272-1065
C-2 Capacitor; 0.1-uF; R/S 272-1432

C-4 Capacitor; 0.22-uF; R/S 272-1070

C-5 Capacitor; 2.2-uF; R/S 272-1435

R-1 Resistor; 10- k; R/S 271-1335

R-2 Resistor; 47-k; R/S 271-1342

VR-1 Variable resistor; 10-k; R/S 271-282 (Note: this
unit cannot be super glued behind a panel hole as
recommended in the text; a different style needed.
S-l Df>or SWITCH

S L K

S-l

-> +5V ifj sry»*/,A/e R(+5to+M

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TYPE 2 TONE DECODER/REJECTOR CIRCUIT
Additional parts required: ,

Ckt Wb-ftb

Svm Description

Q-1 Transistor, NPN; 2N2222A or equiv; R/S 276-2009
R-3 Resistor; 4.7-k; R/S 271-1330

• R-4 Resistor; 10-k; R/S 271-1335

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FEATURE PRESENTATION #2
DATA/TONE SQUELCH CIRCUIT FOR PRO- 2004/5/6

Here's an exceptionally great mod to let the PRO-2004/5/6
recognize worthless computer data and other single or
multiple tore signals and then resume SCAN or SEARCH
within a second or so after locking up on these types of
signals. This mod may resemble the Tone Decoder/Rejector
described above, but they're totally separate circuits
for different applications. The Data/Tone Squelch can
serve in a limited capacity as a Tone Decoder/Rejector,
(i.e, a "Metro-Mod), but it's really for a broader need
to discriminate against many forms of non-voice signals
and not just a specific one like the TOR above. Another
difference is that the TDR will work in most any scanner
whereas the DATA/TONE SQUELCH is only for the PRO-2004,
PRO-2005 and PRO-2006. I am researching ways to apply it
to other scanners, so don't despair if you don't have a
PRO-2004/5/6 at the moment.

The biggest impact of the DATA/TONE SQUELCH is that you
don't have to lockout the Trunked Data Channels anymore
when you're monitoring 800 MHz SMR systems! (The data
channels change every day, anyway, which complicates the
manual LOCKOUT methods on a long term basis.) A scanner
equipped with my DATA/TONE SQUELCH (DSQ) circuit refuses
to lock onto those obnoxious signals as well as cellular
data; most continuous tones; DES/DVP; Improved Mobile
Telephone Service (IMTS) tones and most other non-voice
signals including digital pagers. My DSQ will even
discriminate against static! In other words, my DSQ
discriminates against all but two kinds of signals: voice
and silent or dead carriers! The latter is ok because
the PRO-2004/5/6 SOUND SQUELCH (SSQ) takes care of silent
signals. In fact, my DSQ works with the SSQ but is
independent of it except that the SOUND SQUELCH button on
the front panel activates/deactivates both functions.
Two SPST switches provide independent control of SSQ and
DSQ! Construction/installation of the DSQ are simple and
within the ability of most hobbyists.

STRONG ADVICE: You should have the Service Manual for
your scanner before doing this modification. Order it
from any Radio Shack store or directly from Tandy
Rational Parts Center; (800) 442-2425.

CONSTRUCTION OF THE DATA SQUELCH CIRCUIT

Build the DSQ circuit on perf board about 1” x 1 1 /< ”
though smaller is ok if you are good at micro circuits.
Refer to the pictorials of the parts layout and soldering
plan, Parts List and Schematic Diagram. Use an 1C
socket (XU-1) for U-1 and don't plug U-1 in until the
board has been finished and checked for errors. Don’t
install C-1 on the board but keep it handy for later in
the instructions. Note that Pins 1, 6, 7, 8, 9, 10, 11,
13 & 14 of U-1 are not used. Snip those pins from XU-1
before inserting the socket into the board.

Attach a stiff bare copper wire (#18-#22 ga) to the
ground trace of the board. Loop it through the holes in

the perf board for rigidity and then solder it to the
main ground trace of the DSQ. Leave about 1-inch of this
bare wire free. It will simplify installation of the DSQ
board in the scanner. Solder a RED hookup wire to Pin 3
of XU-1; solder a YELLOW hookup wire to the junction of
D-1 and D-2. Solder a WHITE hookup wire to the anode of
D-4. Solder an ORANGE wire to the cathode of D-4.
Solder a BLUE wire to the cathode of D-3. NOTE: These
wires should be about 6" -8" long.

Construction and layout are not critical and can be
varied from my suggestions which are about as simple as
possible and involve no loops, jumpers or other weird
wiring techniques. Make your board as small as possible,
though, so that it won't take up too much room inside the
scanner. You may be doing lots of modifications in the
future and space might come at a premium. Install the
DSQ Board in an out of the way place, though VR-1 should
be accessible for initial adjustments. The bare ground
wire on the DSQ Board can be soldered to the chassis or
to a printed circuit board ground trace, thereby making
the mount much easier. This bare wire can be bolted to
the chassis if you don't have a heavy duty soldering gun.
Once soldered or bolted, this stiff wire should make the
DSQ Board relatively immobile and stable. You can wrap
the DSQ Board with a layer of clear, plastic tape if
there is a chance of anything shorting to it.

PRO-2004 ONLY: Solder the (+) leg of C-1 directly to
IC-5, Pin 14.

PRO-2005/6 ONLY: Solder the (+) leg of C-1 directly to
IC-5, Pin 7.

PRO-2004/5/6 ALL: Solder the free end of the YELLOW
hookup wire to the (-) leg of C-1. Solder the BARE
ground wire to the chassis or a circuit ground in the
scanner. Solder the free end of the RED hookup wire at
Pin 3 of XU-1 to the OUTPUT leg of IC-8, the +5 volt
regulator on the main chassis of the scanner. IC-8 is
the same in all three scanners, PRO-2004/5/6.

PRO-2004 ONLY: Locate CN-504 on the Logic/CPU Board,
PC-3, and follow its wire bundle back to the top of the
main receiver board. Locate the sky blue (light blue)
wire that connects to the main board at the right end of
the row of wires and desolder that wire from the board.
(This wire comes from Pin 15 of CN-504.) Let it hang
loose for a moment.

PRO-2005/6 ONLY: Locate CN-3 on the main receiver Board
and follow its wire bundle up to the Logic/CPU board.
Locate the sky blue (light blue) wire that connects to
Pin 4 of CN-3. Clip that blue wire halfway between CN-3
and the Logic/CPU Board. Let the two cut ends hang loose
for a moment.

PRO-2004/5/6 ALL: Install two SPST switches of your
choosing in a place of your choosing on the scanner's
front or rear panels. For rear panel installations,
Radio Shack’s micro-mini toggle switches, #275-624, will

be just fine. These switches can also be put into the
front panel, and isn’t difficult to do on the PRO-2004
where there is plenty of room. It is more difficult on
the PRO-2005/6 where the Logic/CPU Board must first be
removed. (See V1N2 of the "HSR" or Vo 1 -2 of my SCANNER
MODIFICATION HANDBOOK for how to do this.) One very neat
choice of switch for any of the PRO-2004/5/6 is a 4, 6 or
8-position DIP switch. The extra switch positions can be
used for other things in due time!

PRO-2004/5/6 ALL: Solder the ORANGE wire of the DSQ
Board to the bottom lug of one switch. This switch will
control the stock SOUND SQUELCH (SSQ) function, on or
off. Solder the BLUE wire of the DSQ Board to the bottom
lug of the other switch. This switch will control the
new DATA SQUELCH function, on or off. Solder a bare
jumper wire from the free lug of one switch to the free
lug of the other switch.

PRO-2004 ONLY: Solder the sky blue wire that was removed
from the main board to the bare jumper wire between the
lugs of the two switches. Solder the WHITE wire of the
DSQ Board to the empty spot on the main scanner board
where the sky blue wire was removed. THIS COMPLETES
INSTALLATION: Proceed to ADJUSTMENT OF VR-1.

PRO-2005/6 ONLY: Splice the WHITE wire of the DSQ Board
to the cut sky blue wire that goes to CN-3 of the main
scanner board. Splice one end of a hookup wire to the
other cut end of the sky blue wire that goes to the Logic
/CPU Board in the front panel. Insulate the splices!
Solder the other end of this new hookup wire to the
common bare jumper wire between the top lugs of the two
switches. THIS COMPLETES YOUR INSTALLATION: Proceed to
ADJUSTMENT OF VR-1.

PRO-2104/5/6 ALL: ADJUSTMENT OF VR-1:

Push the front panel SOUND SQUELCH button ON. Turn the
SSQ switch OFF and the DSQ switch ON. Attach a voltmeter
(-) to ground and (+) to Pin 5 of U-1. Tune the scanner
to a strong, noisy data channel or to a loud, single tone
carrier. (Cellular or trunked data channels are ideal!)
Measure the DC voltage at Pin 5 of U-1, (4.5v typical).
Calculate 80$ of that voltage; then put the voltmeter at
Pin 4 of U-1 and adjust VR-1 for the 80$ level of the
above measurement. Typically, about 3.6 to 3.8v. The
exact adjustment isn’t too critical, but if set too low,
voice signals will resume SCAN or SEARCH. If set too
high, then data 4 tone signals won’t trigger the
SCAN/SEARCH RESUME. Another way to find the optimum
setting is to put a voltmeter (+) on Pin 2 of U-1 and (-)
to ground and tune the scanner to a cellular or trunked
data channel. Adjust VR-1, first one way and then the
other and then to a point so that the voltage on Pin 2 of
U-1 just becomes stable with a nice and steady +5 volts.
It takes a steady 5-volts for about one second to trigger
the SCAN/SEARCH RESUME function, but don't adjust VR-1
any further than necessary to stabilize the DATA/TONE
voltage at Pin 2.

OPERATION & TECHNICAL NOTES: Remember that the SOUND
SQUELCH button on the front panel must be ON before
either SSQ or DSQ can work. The SOUND SQUELCH button is
kind of like a master on/off switch and the two SPST
switches control one, the other or both

Voice signals will cause the scanner to stay locked as
normal until the signal goes away. Minor adjustment of
VR-1 may be necessary for optimum results, but the final
setting will produce a voltage on Pin 4 of U-1 of about
80$ of the peak voltage on Pin 5 of U-1. The DC input
signal at Pin 5 of U-1 will be nearly zero on silent or
quiet signals and about 4 to 4.5v with data & continuous
tone signals. Pin 5 will show a very erratic and rapidly
changing voltage from nearly zero to 4 volts or so for
voice signals. The DC output voltage at Pin 2 of U-1
will be nearly zero on silent or quiet signals; and a
steady +5v with data & continuous tone signals. Voice
signals will cause a rapid fluctuation of the signal
between 0-5 volts at Pin 2 of U-1. When the SOUND
SQUELCH button is off, neither SOUND nor DATA SQUELCH are
operable and scanner operation will be completely normal.

IN CASE OF DIFFICULTY: The most critical part of this
mod is the rectifier circuit consisting of D-1, D-2, R-1,
R-2, C-1 and C-2 and proper pin wiring of the LM-339
chip. Make sure the diode polarities are correct (banded
end is the cathode). Make sure polarities of capacitors
are correct. Tune the scanner to a strong cellular (879
MHz - 881 MHz) or trunked data channel (851 MHz - 866
MHz), and measure the DC voltage at Pin 5 of U-1. There
should be between 4 and 4.5 volts. You won't measure
"too much" but not enough is possible. If so, check the
wiring and components mentioned above. Next most
critical is the polarity and wiring of the two isolation
diodes, D-3 and D-4. Last but not least is the wiring of
U-1. The circuit is so simple and affirmative in its
action that you're not likely to encounter trouble if you
follow these instructions.

Some PRO-2005 (not PRO-2004 or 2006) may have a chirping
or warbling, morse code type of sound on quiet channels
after this mod has been done. If yours exhibits this
weird sound, change C-1 from 1.0-uF to 0.1-uF, Radio
Shack #272-1432. If the "tweet" is still there, then
solder a 1,000-uF capacitor (RS 272-1032) directly to
Pins 4 and 11 of IC-5 in the scanner. Pin 4 should get
the (+) lug of the capacitor while Pin 11 gets the (-).
This is a peculiar problem in some PRO-2005's, but it's
easy to correct so don't worry about it.

If you can't resolve a problem, send me a SASE and one
loose extra stamp with a complete description of the
problem and its symptoms and I’ll respond with written
suggestions and advice. Sorry, no phone calls, please.

THEORY OF OPERATION OF THE DATA/TONE SQUELCH

To understand the simple operation of my DATA SQUELCH, it
is first necessary to understand the PRO-2004/5/6's SOUND
SQUELCH (SSQ) circuit on which we will "piggy back" the

new DATA SQUELCH circuit. The circuits are identical
among the PRO-2004/5/6 scanners but circuit symbols
differ. Bear with me here while I use a simple scheme
for this discussion. P4 means PRO-2004; P5/6 means
PRO-2005 & PRO-2006 and P4/5/6 means ALL.

SOUND SQUELCH THEORY OF OPERATION: A weak portion of
the receiver's audio is sampled at the detector and
amplified through IC-5 ( P4/5/6 ). The highly amplified
audio is fed from IC5, (P4, Pin 1* or P5/6 . Pin 7) to a
rectifier network (P4, D-41 & D-42; or P5/6 . D-43 &
D-44). This rectifier network converts audio signals to
a DC level proportional to the level of the audio signal,
and is used as a bias to turn on or off a switching
transistor, (P4, Q-21; P5/6 . Q-19). Most audio signals
are strong enough to turn the transistor on while very
weak or silent signals keep it off. When the transistor
is off, 5-volts is on its collector, but when the
transistor is ON, the collector drops to nearly zero
volts. 5 volts and 0 volts forms the logic required by
the CPU for making decisions. The collector of the
transistor is fed directly to the CPU, (P4, IC-503, Pin
24; or P5/6, IC-501, Pin 18). When the SOUND SQUELCH
button on the front panel is set to the ON position and
when CPU’s SSQ pin is at zero volts, the scanner SCANS or
SEARCHes as normal, locking on any signals which break
the squelch. Similarly, when the SOUND SQUELCH button is
off, a ground is placed on the CPU's SSQ pin, which keeps
it at zero volts, no matter what.

When the SOUND SQUELCH button is on, and when the scanner
encounters a silent or unmodulated carrier, then the
transistor discussed above gets turned off and a 5-volt
level on its collector is fed to the CPU’s SSQ pin.
5-volts on the CPU's SSQ pin makes the scanner resume
scanning within a second or so after stopping. As long
as there are voices or other audio signals present, the
CPU's SSQ pin will be ”0-v low” and operation is normal.
When that pin goes "+5v high", the CPU is programmed to
resume scanning or searching.

DATA SQUELCH THEORY OF OPERATION: Since the CPU's SSQ
pin responds only to low and high logic and really
doesn't know the difference between voice and data, we
can generate this logic with a separate but opposite
logic circuit to make it discriminate against tones and
data in the same way the SSQ discriminates against silent
carriers. All we need is a circuit that sends a "high”
to the CPU's SSQ pin in the presence of strong, sustained
audio signals such as data or continuous tones. My DSQ
does this nicely, thank you, since voice signals are
erratic, varying, and not at all like data or continuous
tones. C-1 of our circuit samples the same audio as the
SSQ but passes it to a new rectifier circuit, D-1 and
D-2, which with R-l, R-2 and C-2, creates a DC signal
proportional to the level of the audio signal. This DC
signal is fed to Pin 5 of U-1, a Voltage Comparator 1C.
A reference voltage is adjusted by VR-1 and fed to Pin 4
of U-1. As long as the DC signal at Pin 5 is less than
the reference signal at Pin 4, the output of U-1 at Pin 2
will be zero volts "low”. When the DC signal at Pin 5

exceeds the reference voltage at Pin 4, the output of
U-1, Pin 2, will go high to +5v.

The output of U-1, Pin 2 is coupled to the CPU via
isolation diode, D-3. A "high” will tell the CPU to make
the scanner resume SCANning or SEARCH ing while a "low”
does nothing unusual. When VR-1 is correctly adjusted,
the output of U-1, Pin 2 will never go "high" long enough
to trigger the CPU unless data or continuous tones are
present. Strong voice signals may make U-1's output go
high momentarily, but the interval will not be long
enough to trigger the CPU unless the talker does an
extended "Ahhhhhhhhhh" into the mike, because about .5 to
1 sec is required before the CPU will trigger. Most
voice signals of interest will not send a lengthy "high”
to the CPU, but continuous tones and data will! There-
fore, my DATA SQUELCH works just like, though inversely
to the SOUND SQUELCH.

Isolation diodes, D-3 and D-4, allow the SOUND SQUELCH
and the DATA SQUELCH to work simultaneously and not
interfere with each other. Depending on the setting of
the individual DSQ & SSQ switches, both data/tone and
silent signals can cause the scanner to resume SCANning
or SEARCHing, but voice signals will not be affected by
either the SOUND or DATA SQUELCH!

PARTS LIST FOR DSQ CIRCUIT (HOD-44al
Ckt

Syro Description

C-1 1-uF/35vdc Tant; #272-1434; See "Difficulty" text
C-2 2.2-uF/35vdc Tantalum; #272-1435

D 1 -4 1N4148 or 1N914 switching diodes; #276-1122
R-1 390-ohm; #271-018

R-2 12-k; use 10-k + 2.2k in series if need be.

R-3 3.3-k; #271-1328

U-1 LM-339 Comparator; #276-1712

VR-1 10-k ohm trim pot; #271-282

XU-1 1C Socket, 14-pin DIP, for U-1 above; #276-1999

Misc Perf board; #276-1395

Misc Hookup wire; #278-776 or #278-775

SI, 2 Switch, SPST Toggle Switch, #275-624

MERRY CHRISTMAS & HAPPY NEW YEAR

Kell, that's it; we've run out of space and there's still so much more to
write. I am saddened to come to the end of an issue and and the end of a
year and still have items on the list not checked off. In away, it's
called "job security" since a dead end won’t be reached with the next issue.

I laugh at myself now to think about my feelings upon completing Vol-I of my
SCANNER MODIFICATION HANDBOOK . (I wondered if there would ever be anything
else to write about.) I worried about it again last January as we launched
the "KR", but by mid-year, the checklist only got longer and longer after
every issue. One thing grew to inspire another. This spirit is now being
carried into 1992. Ke've only begun! My excitement is rising to a
crescendo over the prospects of what yet lies in store for the radio
monitoring hobby. I hope some of this has rubbed off and renewed or
invigorated your enjoyment and pleasure. A psychic once told me that my
mission in Life is to be at the service of others. It's my fondest hope
that the "fSR" has served your best interests this year, and if it has, my
commitment is to make 1992 even better. Merry Christmas and Happy New Year
to all! 73/bc S Staff

WIRING & COMPONENT PLACEMENT DIAGRAMS FOR DATA/TONE SQUELCH (MOD-44a)

COMPONENT

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CONFIDENTIAL SUBSCRIPTION ORDER: Please print clearly

V 1 N 1 0

10/26/91 SUBSCRIPTION RATES 4 ORDER BLANK V1N10

NAME:

USA RATES: (Canada + 10% ; Other Foreign +20%-surf or HflVAir)

*SR BACK ISSUES ONLY USA $$ Check Items

STREET:

1991 Single copies; your choice: 1 ea $ 4 . 00
1991 (1st 6-mos, Jan-Mav/Jun) 5 ea $15.98

CITY: STATE: ZIP:

1991 (2nd 6-mos, Jul-Nov/Dec) 5 ea $15.96

199! (1st Year, Jan-Nov/Dec) 18 ea $25.88

PHONE :( 1 AMT ENCLOSED: $

m CURRENT SUBSCRIPTIONS ONLY

1322 Single copies; your choice: 1 ea $ 4.00

THE BELON QUESTIONS ME OPTIONAL BUT HILL HELP US HELP YOU!

1992 (Jan-May/June) 6-mos 5 ea $15.80

Radio Interests? (Put YEARS OF EXPERIENCE in each block that applies)
VHF-UHF Amateur CB Shortwave Professional
Scanning? Radio? Radio? Listening? Radio?

1992 (Jan-Nov/Dec) 1-yr 10 ea $25.00

1992-3 (Jan 92-Nov/Dec 93) 2-yr 20 ea $45.00
OTHER LITERATURE AVAILABLE

Career/Profession
Or OccuDat ion :

HOBBY RADIO BUYER'S DIRECTORY $14.95 ppd surf

SCANNER MOD HNDBK. Vol-1: $11.95 > $3.00 S&H *

List makes & models of your scanners S other radio equipment:

Describe your technical abilities & interests; use reverse as needed.

SCANNER MOD HNDBK. Vol-2: $17.95 + $3.00 S&H *

* Canada USU SBH; Other Foreign US$5 SSH; extra for Air Hail

MAKE REMITTANCE PAYABLE IN US FUNDS TO: COHHTRONICS ENGINEERING

Enclose a #10 S’.A.S.E. and one loose extra stamp if you want
hobby in f o & persona! reply! Business/trade inquiries exempt.

'/VA/h £ec&)0&£j

XC-&CAU.)'

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SCHEMATIC DIAGRAM FOR DATA/TONE SQUELCH CIRCUIT (M00~44a

(j£CLO<n)

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XC- 501 ~ PRO -2005/6

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(Lode/ CPU 36 API)')

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COMMTRON I CS ENGINEERING
"THE WORLD SCANNER REPORT"
PO BOX 262478
SAN DIEGO, CA 92196-2478

V 1 N 1 0
911026

IN THIS ISSUE

FIRST CLASS HAIL

+ Easier to understand subscription blank
t Last Call to Renew for 1992!

+ HSR Hants to Buy a Real Cheap Computer!

+ The Latest On Computer Interfaces from
DataMetrics, RH Systems, and others
♦ Serial CPU Data Interceptor /Decoder for PRO-2WJ4/5/6
+ Tone Decoder/Rejector (MetroMod) For All Scanners
+ Data/Tone Squelch (MOD-44a) for PRO-2004/5/6

+ SUBSCRIPTION EXPIRES? RENEW SOON l

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